Shaping the Plasmonic Response: Hollow Gold Elliptical Nanotubes

Highly tunable localized surface plasmon (LSP) resonances in metal nanostructures are of great importance for manipulating light waves and enhancing light-matter interactions at the nanoscale. Here, a new type of plasmonic resonators based on hollow elliptical nanotubes, which can generate highly tunable LSP resonances in the visible frequencies, are reported. High-quality hollow gold (Au) elliptical nanotubes with fine controllable size and morphology are experimentally fabricated. Dark-field scattering measurements reveal the presence of multiple plasmon resonances including longitudinal Fabry-Perot resonances and transverse hybridized LSP resonances due to rotational symmetry breaking. Upon varying the ellipticity, the hybridized LSP resonances exhibit continuously spectral evolution behaviors, such as the hybridized modes shifting and crossing. The experimental results show good agreement with the rigorous electromagnetic modeling and Raman spectroscopic measurements. The hollow anisotropic geometries provide highly tunable plasmonic responses together with homogeneous field distributions and high surface-to-volume ratio, which hold great potential for practical applications in sensing, nonlinear optics, surface-enhanced spectroscopies, and bio-medicine.